When the Reich team applied this method to 91 ancient individuals for whom it had sequenced enough of the genome to carry out this analysis, it found 19 pairs of DNA cousins living on different large islands or island groups in the Caribbean: for example, an individual in Hispaniola with a cousin in the Bahamas, and another individual in Hispaniola with a cousin in Puerto Rico. This meant that the entire population had to be very small; you wouldn’t find that random pairs of people had such a high probability of being closely related if the entire population was large. (To put this in perspective, if you did the same analysis on random pairs of people across China today, DNA cousins would be detected many thousands of times less often.)
The rate of close relationships that the Reich team found is what would be expected for about 3,000 people — at most 8,000 people — in their childbearing years in Hispaniola. The true numbers of people could have been threefold to tenfold larger because at any given time only a fraction of a population is in its childbearing years. Still, we can confidently conclude that the pre-contact population size of Hispaniola was no more than a few tens of thousands of people.
This is a classic ancient DNA surprise — the kind of unexpected finding this new technology has shown repeatedly that it can deliver. For example, the sequencing of a finger bone from Siberia thought to be from a modern human turned out to be from an archaic population not previously known to archaeologists, or even hypothesized by them. Such results emphasize how much we still have to learn about the past.
How should the new findings change the way we think about the fate of Indigenous people in the pre-contact Caribbean? In some ways, not at all. Whatever the starting population, what happened to Indigenous Americans after Europeans arrived amounted to genocide: the systematic obliteration not just of individuals but also of their culture and community — what the philosopher Claudia Card called the “social death” at “the center of genocide.”
Even if you focus more narrowly on statistics, the numbers of deaths in both absolute and relative terms are horrific. According to a 1540 census, the number of Indigenous people in Hispaniola had dropped to 250 people. It dropped to zero in later counts.
In other ways, however, ancient DNA research significantly changes how we think about Indigenous people in the pre-contact Caribbean. Another surprising finding, for instance, is that the genetic legacy of pre-contact Caribbean people did not disappear: They contributed an estimated 14 percent of the DNA of living people from Puerto Rico, 6 percent of that in the Dominican Republic and 4 percent of that in Cuba. In addition, by illuminating the highly mobile lifestyle of pre-contact Caribbean people with many DNA cousins across different islands, the research underscores the degree to which they were connected — a relative unity later fractured by centuries of division into colonial spheres by European powers.
Colonization resulted in such immense destruction that the rich cultures of the pre-contact Caribbean can be reconstructed only through a blend of oral traditions and scientific study, including the new insights provided by ancient DNA analysis. It is a blessing to be able to get closer to this heritage. And it is the loss of the people and cultures that produced this heritage that most provokes our outrage.
David Reich, a professor of genetics and human evolutionary biology at Harvard, is the author of “Who We Are and How We Got Here: Ancient DNA and the New Science of the Human Past.” Orlando Patterson, a professor of sociology at Harvard, is the author, most recently, of “The Confounding Island: Jamaica and the Postcolonial Predicament.”
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